1. Field of the Invention
This invention relates generally to microorganisms, and processes employing microorganisms, having the ability to interact with organic sulfur found in carbonaceous materials.
2. Prior Art
The prior art teaches that bacteria which are found in acid coal mine drainage ditches are capable of removing inorganic sulfur (i.e., pyritic sulfur from coal by oxidation) producing sulfuric acid. For example, the article "Coal Desulfurization by Leaching Involving Acidophilic and Thermophilic Microorganisms", Biotechnology & Bioengineering, XXIV (1982), 743-748, discloses that the bacterial agent Thiobacillus ferrooxidans interacts with the inorganic pyritic sulfur associated with coal according to a reaction sequence which proceeds as follows: EQU FeS.sub.2 +3.5O.sub.2 +H.sub.2 O.fwdarw.FeSO.sub.4 +H.sub.2 SO.sub.4 [ 1] EQU FeS.sub.2 +3O.sub.2 +2H.sub.2 O.fwdarw.2H.sub.2 SO.sub.4 +Fe.sup.3.spsb.+[ 2] EQU FeS.sub.2 +Fe.sub.2 (SO.sub.4).sub.3 .fwdarw.3FeSO.sub.4 +2S [3]
The aforementioned reaction mechanism operates on inorganic sulfur only. Efforts to remove organic sulfur with this pyritic sulfur-removing bacteria have not been successful.
In an item in the publication Fuel, 58 (1979), 549-550, Chandra, et al., preliminarily reported microbial removal of organic sulfur from coal using Thiobacillus ferrooxidans. In a later publication, however, Fuel, 59 (1980), 249-252, Chandra, et al., report good inorganic sulfur removal and poor organic sulfur removal using a microorganism, presumably, Thiobacillus ferrooxidans. The article "Microbial Oxidation of Dibenzothiophene by the Thermophilic Organism Sulfolobus Acidocaldarius", Biotechnology and Bioengineering, XXVI (1984), 687-690, discusses Sulfolobus acidocaldarius, a thermophilic (60.degree.-90.degree. C.) reduced sulfur and iron oxidizing microorganism, that is a facultative autotroph. The microorganism was originally isolated from the acidic hot springs of Yellowstone National Park. Several high-temperature (70.degree.-90.degree. C.) strains of Sulfolobus have been isolated. The organism is acidophilic with a pH optimum of 2&lt;pH&lt;3 and is capable of using both reduced inorganic substrates (Fe.sup.2.spsb. and reduced sulfur) and simple organic (carbohydrate) compounds as a source of energy. The organism has been used for sulfur (mainly pyritic sulfur) removal from coal and metal leaching from certain mineral sulfides.
This article reports an investigation of the oxidation of dibenzothiophene (C.sub.12 H.sub.8 S) using the thermophilic Sulfolobus acidocaldarius microorganism in a nutrient medium with dibenzothiophene as the sole source of carbon.
The article reports Sulfolobus acidocaldarius is capable of oxiding sulfur present in dibenzothiophene to sulfate. In addition, the article suggests that as a microorganism capable of oxidizing dibenzothiophene, Sulfolobus acidocaldarius may prove to be effective in removing thiophene compounds from waste water streams, coal and crude oil.
It is by no means obvious, however, that a microorganism which can oxidize pure dibenzothiophene would be effective in removing thiophene compounds from waste water streams, coal or crude oil. Actual effectiveness in these applications can only be shown by actual trials demonstrating such effectiveness.
Identification of microorganisms which can oxidize and/or aid in removal of organic sulfur from carbonaceous materials such as coal, petroleum coke and petroleum oils would be very desirable.